Tucson

More March Madness – AZ Star blames human-caused climate change for March heat

On Sunday, April 30, the Arizona Daily Star published a front-page story by Tony Davis which proclaimed “Greenhouse gases called a factor in March heat.” (Link to online version)

The story begins: “Human-caused climate change was at least partly to blame and probably mostly to blame for Tucson’s record-setting March heat, says a researcher with expertise in this field.”

This story is another example of speculation based on computer modeling and cherry-picked data rather than physical evidence. The Star consulted Dr. Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute who analyzed possible factors for explaining Tucson’s March temperatures. “He concluded that long-term temperature trends point almost certainly to human-caused greenhouse-gas emissions as a factor. The unresolved question, he said, is how big of a factor they are.” The article provides no physical evidence to support that conclusion.

Ignoring the high temperatures during the 1900s to 1930s, van Oldenborgh examined the record beginning in 1950 and found “a clear upward trend in the March high temperatures started in the middle 1970s.” (See my article: March 2017 – Hottest Ever in Tucson? for earlier temperature data. That article shows Tucson’s temperatures steadily rising, probably due to the urban heat-island effect, while temperatures in rural Tombstone remained level.)

From the Star: “Looking across Southern and Central Arizona high temperatures for March, van Oldenborgh found they seem to be warming across the region but that Tucson’s temperatures are rising faster than in nearby cities Casa Grande and Willcox.”

“The urban heat-island effect often accounts for differing temperatures between larger and smaller cities. But van Oldenborgh said he tried to account for such differences by focusing his analysis on daytime high temperatures, not nighttime lows that are most commonly affected by the heat island effect.” So he didn’t study the heat island effect.

Oldenborgh looked at computer models. One model set “showed that March high temperatures have risen at a point near Tucson at about 2.5 times the rate the global average temperature has risen since about 1950. The model shows that is the local effect of global warming.” (A new term: local global warming?) The other model set “showed that Tucson has received on average less long-term warming than shown by the first model.”

The article contained much “expert” speculation, but from the material presented, I see no physical evidence justifying the conclusion nor the headlines that could attribute the high March temperatures to carbon dioxide emissions. If it was not just a quirk of natural variation, then maybe Tucson has its own evil cloud of carbon dioxide hovering above the city. Of course, there was lots of hot air expelled by local politicians in March.

In my opinion, this type of story is, to put it politely, junk science, designed to stir up alarm about a subject that has become purely political. It is not really news, but propaganda.

Here is the temperature record from the USHCN weather station at the University of Arizona. The top red line shows March high temperatures. The other lines show a slow rise consistent with the urban heat island effect. Had van Oldenborgh used this more complete record, his “clear upward trend” would have disappeared.

See also:

Evidence that CO2 emissions do not intensify the greenhouse effect

Also look at this story from 2012: MILD WINTER MAKES MARCH MADNESS
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Tucson Mountains geology – an update

TucsonMtns03

The Tucson Mountains form the rampart on the west side of the city. If you drive over Gates Pass, take a look at the road cuts, especially near the top, you will see a chaotic jumble of different rocks, mainly volcanics. According to the Arizona Geological Survey: “Tucson Mountain Chaos is a formal geologic name, describing one of the more confusing, complex, and controversial areas in southern Arizona.”

Like many mountain ranges in Southern Arizona, the Tucson Mountains have experienced several episodes of volcanic eruption. Major eruptions occurred during Triassic-Jurassic time (~190-200 Ma), early Laramide (74 Ma), later Laramide (62 Ma), and one late Tertiary (~20 Ma). (Ma means million years ago.) There were also several interspersed minor eruptions.

The early Laramide (74 Ma) eruption was very explosive and produced great volumes of rhyolite tuff (Cat Mountain tuff). The rapid eruption caused the volcano to collapse in on itself to form a caldera. That collapse produced megabreccia called the Tucson Mountain Chaos. (Breccia is simply a bunch of angular fragments cemented together.) Within that breccia are small to very large fragments of other rocks including house-sized blocks of limestone. The breccia could have formed in three ways (and there are proponents of each way): moat in-filling of the caldera, landslides, or fluidized material brought up from below.

TM geo map3The Tucson Mountain caldera is not a typical caldera with equal subsidence all around. Rather, it is a “trap door” caldera with the “hinge” area on the southeast and major subsidence on the west. The western ring fault (called the Museum Fault) parallels Kinney Road from about Old Tucson to just past the Arizona-Sonora Desert Museum, then swings east around a granite pluton. This structure was first proposed by Peter Lipman of the United States Geological Survey in 1994 and later supported by geophysical investigations.

Beginning about 25 to 30 million years ago, Arizona and the West experienced crustal stretching which began to tear things apart. It was proposed, about 10 years ago, that the Tucson Mountain volcano and caldera formed over where the Santa Catalina Mountains now stand on the east side of Tucson. It was posited that crustal stretching slid the caldera to its present location. (You can see an explanation and cross-sections of that story in a 2009 article from my Wryheat blog.) That was such a neat story that the Arizona-Sonora Desert Museum constructed a mechanical model which Docents (including me) used to interpret the story. That particular “kit” has been retired because subsequent evidence shows that the story is probably in error. The main evidence against the sliding story is that the chemistry of the volcanics in the Tucson Mountains is incompatible with the proposed generating pluton in the Santa Catalina Mountains. There are also some structural inconsistencies.

TM section

One other thing: there was a Tucson Mountain dinosaur. Dinosaur bones were found within one of the blocks of megabreccia about 1800 feet NNW of Gates Pass. This dinosaur is classified as a large Hadrosaur (duck-billed dinosaur). This dinosaur lived in Tucson some time between 72 and 83 million years ago.

References:

Kring, D.A., 2002, Desert Heat – Volcanic Fire, The Geologic History of the Tucson Mountains and Southern Arizona, Arizona Geological Society Digest 21

Lipman, Peter, 1993, Geologic map of the Tucson Mountains Caldera, southern Arizona, U.S.G.S. IMAP 2205. (link)

Lipman Peter W., 1994: Tucson Mountains caldera; a Cretaceous ash-flow caldera in southern Arizona. U S (link)

Marshall, L. and Stokes, P., 2012, the Tucson Mountains Caldera: Using Gravity and Magnetic Anomalies to Test Trapdoor Subsidence and Locate Subsurface Plutonic Bodies. (link)

Spencer, G.L. et al., 2005, The late Cretaceous Tucson Mountains dinosaur, New Mexico Museum of Natural History and Science Bulletin, 29 (link)

See also:

Arizona Geologic History: Chapter 1, Precambrian Time When Arizona was at the South Pole

Arizona Geological History: Chapter 2, Cambrian and Ordovician Time

Arizona Geological History: Chapter 3: Devonian to Permian Time

Arizona Geological History Chapter 4: Triassic Period

Arizona Geological History Chapter 5: Jurassic Time

Arizona Geological History Chapter 6, The Cretaceous Period

Arizona Geological History Chapter 7: The Cenozoic Era

Old mines of the Tucson Mountains

2015 was rainiest year at my house

Even though the southwest is experiencing drought conditions, 2015 was the rainiest year in the last nine years during which I recorded rainfall at my house.

Since mid-2007, I have been measuring and reporting daily rainfall at my house on the west side of Tucson, Arizona. This is part of the RainLog.org program run by SAHRA, “Sustainability of Semi-Arid Hydrology and Riparian Areas.”

Tucson has two rainy seasons: a winter season which may or may not have much rain, and the summer monsoon which gives us the majority of rainfall in the region. During the winter, our weather comes from the west and storms may be sucked dry as they pass over the Sierra Nevada of California. During the summer, our weather comes from the southeast with winds bearing moisture sucked out of the Gulf of Mexico and the Gulf of California.

See Anatomy of a Thunderstorm and The North American Monsoon

During the summer monsoon, desert heat and orographic uplift from mountain ranges turn that moist air into thunderstorms. In Tucson, much of the rain occurs on the east side of town because of the air flow direction and orographic uplift over the Catalina Mountains. We who live on the west side of town get what is left over.

Here are the numbers.

In 2015, I recorded 14.32 inches of rain. The next rainiest year was 2008 with 12.09 inches. The dryest year was 2013 with 7.95 inches. The graphs below from RainLong show how rain occurred during the year (there are two graphs because Rainlog can plot only five years at a time).

MyRain 2008-2010

MyRain2011-2015

Here is the total rainfall recorded in inches since 2008:
2008: 12.09
2009: 10.00
2010: 11.56
2011: 10.83
2012: 10.85
2013: 7.95
2014: 11.36
2015: 14.32

As I write this on January 2, 2016, El Nino driven rain is forecast for every day next week.

 

Is a proposed Tucson Metropolitan microgrid of solar energy a good idea?

A guest opinion in the Arizona Daily Star (Jan. 23, 3015) by Terry Finefrock proposed that Tucson build a system of photovoltaic solar energy facilities and connected electrical storage units (see article here). Finefrock claims “By using rapidly developing energy storage equipment on feeder circuits we can manage fluctuations in demand or supply, essentially creating a metropolitan microgrid.” He also claims that photovoltaic generation of electricity is less expensive than fossil fuel generation.

I emailed him asking what”rapidly developing energy storage equipment on feeder circuits” was and whether such equipment is at a stage sufficient for commercial deployment. He responded the same day referring me to http://www.greentechmedia.com/. The answer seems to be a whole bunch of batteries.

At the website, I found a story on British pumped hydro storage (not likely to work in Tucson); a story saying “General Electric is significantly scaling back production of its sodium-ion Durathon batteries, a move that comes amid what the company says is a slow-to-develop market for grid-scale energy storage”; and a story on “Faulty Solar Panels Are Creating ‘Uncertain Risk’ for Chinese PV Projects.” I searched the site for the word “storage” and got several more articles about batteries connected to the grid.

I know from other sources that several schemes are in the works. For instance, a solar-thermal plant in Gila Bend proposes to store excess heat in molten salt containers that they claim will provide 12 hours of generation. Tucson Electric Power was also planning a solar-thermal system with heat storage in Tucson. But what happens if it is cloudy two or three days in a row?

The biggest problems with solar and wind electrical generation, other than cost, is their intermittency and unreliability. Solar panels can deliver significant energy only from 9am to 3pm on a clear day – a maximum of 25%of the time. A good storage system for electricity could possibly help extend that time, but much of solar’s peak generation would need to be used for recharging the storage equipment rather than providing for consumer demand.

Typically, solar systems provide less than 25% of their rated capacity whereas fossil fuels provide at least 85% of their rated generating capacity according to the Energy Information Administration (EIA). This is what EIA calls capacity value “which depends on both the existing capacity mix and load characteristics in a region. Since load must be balanced on a continuous basis, units whose output can be varied to follow demand (dispatchable technologies i.e. fossil fuels and nuclear generation) generally have more value to a system than less flexible units (non-dispatchable technologies such as solar and wind), or those whose operation is tied to the availability of an intermittent resource.”

Dr. John Morgan, Adjunct Professor in the School of Electrical and Computer Engineering at RMIT (Australia), claims “energy storage cannot solve the problem of intermittency of wind or solar power. Not for reasons of technical performance, cost, or storage capacity, but for something more intractable: there is not enough surplus energy left over after construction of the generators and the storage system to power our present civilization.” Morgan claims that the energy required to manufacture and operate solar photovoltaic systems and battery storage for electricity is about equal to the energy produced over the life of the facility, so there is little to no net energy produced. (See article here)

In the Star article, Finefrock claims that solar energy is less expensive than coal or natural gas fueled generation, but he seems to ignore manufacturing and capital costs for solar systems and batteries.

The U.S. Energy Information Administration (EIA) takes a different view when comparing energy sources. They use a metric called “Levelized cost of electricity (LCOE)” which “represents the per-kilowatt-hour cost (in real dollars) of building and operating a generating plant over an assumed financial life and duty cycle. Key inputs to calculating LCOE include capital costs, fuel costs, fixed and variable operations and maintenance costs, financing costs, and an assumed utilization rate for each plant type.”

In EIA’s latest report, they estimate LCOE for solar photovoltaic to be 230 $/MWh, and solar thermal at 243 $/MWh versus 96 $/MWh for conventional coal and 66 $/MWh for conventional natural gas.

As to the question in the article title, a microgrid connected storage system is technologically possible, but given the facts that solar energy is unreliable and expensive; that storage equipment is expensive and could provide a backup for only a limited time; and that a very large number of batteries to make it beyond a few days would take most of the PV output to charge them, it makes little sense to retire fossil-fuel fired plants in favor solar energy as Finefrock suggests.

UPDATE:

From Carmine Tilghman is senior director of wholesale, fuels and renewable energy for Tucson Electric Power in response to editorial by Terry Finefrock:

“We must also abide by economic realities and proven facts, including the higher cost and lower reliability of solar power. Such concerns do not burden everyone who takes an interest in energy issues. Last week, a Terry Finefrock (“Economic development: Start with a Tucson microgrid,” Jan. 23) offered a series of misleading assertions about energy costs and issues. Energy-storage systems are not yet capable or cost-effective enough to provide an alternative to the constant support and backup capabilities of a utility’s local electric grid.” Read full article at http://tucson.com/news/opinion/column/guest/response-to-assertions-made-about-energy-s-costs-systems/article_c6bda9a8-6bd7-52f9-a08d-99f823e608db.html

See also at the Arizona Daily Independent:

Impact of Solar and Wind Electricity Generation – the European experience is that “green” energy is turning out to be 10 to 100 times more expensive that originally thought.

Top Google Engineers Say Renewable Energy ‘Simply won’t work’

Avian mortality from solar farms

See more on Wryheat::

Solar energy cannot economically compete in electricity generation

The economic impact of Arizona’s renewable energy mandate

Does alternative energy actually replace fossil fuel consumption? In a study from 130 countries, it was found that each unit of electricity generated by non-fossil-fuel sources displaced less than one-tenth of a unit of fossil-fuel-generated electricity.

The old Jacobs tungsten mill in Tucson

The Jacobs tungsten mill, located northwest of the intersection of Speedway and Silverbell, about 2 miles west of downtown Tucson, processed tungsten ore during World War 2. The ruins of the mill remain on-site.

Jacobs2

Arthur Jacobs entered into a contract with the U.S. military to process tungsten which is a strategic metal used as an alloy to “harden” other metals, and to make armor and artillery shells.

The mill was operated under great secrecy, perhaps explaining why it was not listed in city directories at the time. Loads of processed ore were delivered under armed guard in government trucks to the Southern Pacific freight depot and shipped to Kansas City in special unmarked cars. Despite war rationing of gasoline, the mill and Arthur Jacobs Sr. were allotted an ample supply in order to run the mill.

The property is owned by the City of Tucson. In the mid-2000s, the City contemplated turning the property into “Painted Hills Natural Resources Park.” However, soil samples showed elevated levels of lead, arsenic, and cadmium. The City spent $200,000 for soil sampling, which one source says was bond money, while another source claims was a grant from the EPA.

A health consultation by the Arizona Department of Health concluded that these elevated heavy metals in the soil posed no danger to adults, but could prove dangerous to young children if they ate large quantities of dirt. They recommended that the site be remediated before use as a recreational park. The City has done no remediation on the site to date to my knowledge.

None of the reports says where the tungsten ore came from, but there are many tungsten deposits in southern Arizona. My guess is that the ore came from the Campo Bonito area in the Northern Santa Catalina Mountains and from the Little Dragoon Mountains (north of I-10, between Benson and Willcox. Another possibility is the Las Guijas mountains near Arivaca since there is reported tungsten production in the 1930s.

According to Wilson (1941): The principal tungsten minerals found in Arizona are the wolframites (ferberite, wolframite, and huebnerite); scheelite; powellite; cuprotungstite; and tungstite. Only the wolframites and scheelite have been of commercial importance. In Arizona, the principal source is tungsten-bearing quartz veins and shear zones in rocks that have been invaded by granite, granodiorite, pegmatite, or latite. A few placers, as in the Little Dragoon and Camp Wood areas, for example, have yielded notable amounts.

Lode and placer deposits from the Little Dragoons produced 55,000 pounds of concentrate during World War I and into the 1930s.

Mines in the Camp Benito area produced gold and tungsten intermittently since 1908. The gold may have contributed to the placers in Canada del Oro (see my article: The Gold of Cañada del Oro). Some of the claims were known to produce tungsten in 1941. Some production is reported in the late 1930s and early 1940s from mines near Mammoth, a few miles northeast of the Camp Benito area.

I have attempted to find out if Tucson still intends to clean up the area and create a park at the site, but I have been unsuccessful in reaching a knowledgeable City official.

References:

Archaeological survey 2006:

http://www.tucsonaz.gov/sites/default/files/esd/arc_final.pdf

This reference contains maps and many photographs of the mill ruins.

Health assessment The Arizona Department of Health and Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services in 2008:

http://www.azdhs.gov/phs/oeh/pdf/old_tungsten_mill_9508.pdf

Tungsten Deposits of Arizona

By Eldred D. Wilson, 1941 http://repository.azgs.az.gov/sites/default/files/dlio/files/nid1245/b-148.pdf

P.S. I asked the City about the status of the park project, here is their response:

Here are the responses to your questions that were forwarded our Environmental Services Department.

My questions:
1. Has the area in fact been cleaned up?
This area has not been abated. Impacted soils are still in place within the few areas on the site. City has installed fencing to prohibit public access and other preventive measures to contain soils from migrating off site.

2. If so where was the contaminated soil disposed?
No, soils are still in place as stated in response to Question 1.

3. Does the City still plan to establish a park there?
It is unknown at this time. The city hopes to abate this site as needed when funding is available. This property is owned by Parks and Recreation Department (P&R). Environmental Services does not know what P&R future plans are to develop this site as a natural park.

4. What is the status of the project?
Through an Environmental Protection Agency (EPA) Brownfields Cleanup grant the City of Tucson (City) completed an Analysis of Brownfields Cleanup Alternatives (ABCA), in December of 2008, which determined the most cost-effective and practical methods to remediate the site. In addition, in November of 2010 a Remedial Workplan was prepared and submitted to the Arizona Department of Environmental Quality (ADEQ) under the Voluntary Remediation Program. The selected remedial (cleanup) action alternative for this site recommended consolidation of the impacted soil within the limits of the former mill site footprint, and install an engineered soil-cover with clean soils. However, the cost of this remediation alternative is estimated to be $800,000, which far exceeded the City’s EPA Brownfields Cleanup grant of $200,000, and the City’s current budget capacity.

At this time, the Parks and Recreation Department does not have adequate funding to cover the associated costs for remediation of this site. The site is secured with a chain linked fence, which prohibits public access. Under ADEQ stormwater guidelines, the ADEQ – Southern Regional Office, Compliance Programs Unit approved the City’s Stormwater Pollution Prevention Plan (SWPPP), which outlines measures to prevent impacted soils from being transported via future stormwater runoff. In March 2014, the City completed the installation of preventive measures (Best Management Practices) as outlined in the SWPPP. The corrective measures will prevent impacted soils from leaving the site through the installation of waddles, and silt screens, and ensure these areas are contained onsite until funding for remediation is available.

You may contact Parks and Recreation directly if you would like more information regarding the future plans of this site.
David Barraza
City of Tucson
Environmental Services

Tucson transitioning to a renewable water supply

The state of Tucson’s water supply is always a concern. So how are we doing? Recently, Docents at the Arizona Sonora Desert Museum had an update by Wally Wilson, chief hydrologist at Tucson Water. The reason is that we Docents often have to explain to museum visitors what all those rectangular ponds are doing in Avra Valley just west of the museum. The following material is taken from his talk.

Tucson gets water from four sources: pumped groundwater, water transported from the Colorado River via the Central Arizona Project canal (CAP), water reclaimed from sewers, and water treated from former industrial usage (Tucson Airport Reclamation Project, TARP). Water is measured in Acre-feet (AF). One AF is 325,851 gallons and one acre-foot will serve four residences in Tucson for a year. Mr. Wilson presented the following graph on water usage (as of 2011):

Transition-to-renewable-supplies

Notice that total water usage has been declining and has reached the level it was in 1994.  That was surprising to me. Perhaps our conservation efforts are paying off. Mr. Wilson noted that average residential use in Tucson is about 90 gallons per day per capita (versus 200 in Scottsdale). Tucson is conserving groundwater by using more and more CAP water. This graph shows that our groundwater use has declined to what it was in 1959 in spite of our increasing population.

In 2011, CAP supplied 64% of our water while groundwater supplied 20%. The remainder was made up of reclaimed water. Total production in 2011 was 120,350 AF. In 2013, Mr. Wilson expects CAP will supply 80% of our needs allowing us to decrease primary groundwater pumping.

Below is a map of the CAP system. It consists of ponds to recharge the aquifer, wells to pump the water, a treatment plant, and a reservoir which stores 60 million gallons.

Clearwater-map

There are three recharge areas which Tucson Water fondly calls CAVSARP, SAVSARP, and PMRRP. These are the areas featuring recharge ponds filled with CAP water and wells to reclaim the water after it recharges the aquifer.

Why put the water in ponds to sink into the aquifer rather than treating it and pumping it directly to consumers? There are several reasons. When we first began to receive CAP water it was treated and sent to households, but the water wreaked havoc with some of our old plumbing. The current system is plan B and it has several advantages besides being kinder to plumbing.

Water from the ponds sinks into the ground at the rate of about 1.5 feet per day. As it travels 300- to 400 feet to the water table, soil filters out any viruses and bacteria that may be in the water. This filtering method is much less expensive than disinfecting the water in a treatment plant. The water still goes through the Hayden-Udall treatment plant for filtering and chlorination.

Some numbers: CAVSARP recharges 70,000 to 80,000 AF/year and recovers 70,000 AF/year. SAVSARP is permitted to recharge 60,000 AF/year and recovers about 15,000 AF/year. We are still ramping up to use our total CAP allocation. PMRRP is permitted to recharge at the rate of 30,000 AF/year and recovers water at 14,000 AF/year.

Tucson Water claims that it loses about less than 2% of the water due to evaporation from the recharge ponds. The overall CAP system loses about 5% of its water due to evaporation. Most of that occurs in Lake Pleasant which acts as a storage buffer between supply and demand.

Mr. Wilson says Tucson will have plenty of water through 2050 and beyond because we are banking water in the recharge system (and we still have the groundwater). Tucson Water is also pursuing additional sources of renewable water such as water owned by Indian Tribes. For more information see http://cms3.tucsonaz.gov/water .

See also my older posts on our water supply:

Water Supply and Demand in Tucson

How much water is there?

Trends in groundwater levels around Tucson

EPA war on coal threatens Tucson water supply

Book Announcement – The Mosaic Murder by Lonni Lees

Mosaic Murder coverThe Mosaic Murder is a new mystery by Tucson writer Lonni Lees.

Synopsis by Borgo Press:

“The artists’ reception at the popular Mosaic Gallery in Tucson, Arizona is a great success, but the next morning, when the body of Armando, the owner’s husband, is discovered, things start turning ugly. Every artist becomes a suspect, and each of them has their own reason to want the man out of the picture. But who disliked him enough to want him dead? And who stole the Mexican artifacts and the sculpture of the goddess Gaia? Gallery owner Barbara Atwell is devastated at her young husband’s death, and turns to her friends, Adrian and Rocco, for support. An unseasonal Arizona heat wave keeps everyone’s nerves on edge as Police Detective Maggie Reardon juggles a disastrous personal life while trying to solve the crime. She even finds herself attracted to one of the suspects as she sifts through a long list of colorful, Bohemian characters to determine who had the ultimate motive for murder. But when she’s viciously attacked in her own home, she begins wondering whether she’ll survive long enough to find the culprit. The first of a great series of detective novels set in the sizzling Southwest!”

Review by Terry Butler, artist and writer:

“This is Lonni Lees’ third book and her second novel. I’ve had the pleasure of reading them all as well as her online and print stories, but I have to say this one is my flat-out favorite.

“Lonni lives in Tucson and writes her descriptions of the area and its harsh beauty, plants and weather with a sure hand. And the best thing about that is her exercise of self control, showing us that the right amount of atmosphere is just enough, leaving her room to draw the character of Detective Maggie Reardon in detail–flaws and strengths alike, just as in all human beings. Maggie is no superhero hard-boiled dudette in sexy clothes, but a smart, interesting woman whom we end up caring a great deal about.

“In fact all the characters in this book are well described and believable, even if some of them are a bit weird. But then, who are artists and gallery hangers-on if not umm, “unique” individuals? Its a great milieu for a mystery and Lonni keeps us guessing all the way.

“It’s great to see a new writer getting this much better with each outing, and word is that Lonni has another of Detective Reardon’s adventures in the pipeline. I’ll be waiting!”

This book has just been released and is available at Amazon   as a print book and Kindle. It will soon be available from other providers. Other books by Lonni include Deranged, a novel of horror and Crawlspace, an anthology of creepy short stories.

The Pirate Fault of the Santa Catalina Mountains

The Pirate fault on the west side of the Santa Catalina mountains defines the western escarpment of the range and parallels Canada del Oro wash.

The Arizona Geological Survey has just published a new paper on the fault:

Citation: Hoxie, D.T., 2012, Exhuming the Remains of the Inactive Mountain-Front Pirate Fault, Santa Catalina Mountains, Southeastern Arizona. Arizona Geological Survey Contributed Report CR-12-F, 18 p. You can download the 24Mb report here.

Pirate-fault-zone

The Arizona Geological Survey describes the Pirate fault system as follows:

Not so long ago, mountain building was alive and well in southern Arizona. [The Pirate] fault demarcates uplift of the Santa Catalina structural block to the east, from the down-dropped, alluvial Cañada del Oro basin to the west. Vertical displacement on the nearly 16 mile long fault is about ~ 2.5 miles or 13,200 feet, which occurred over a six million year span from ~ 12 to 6 million years before the present.

Once buried under detritus eroded from the uplifted Santa Catalina Mountains, the Pirate fault is currently being exhumed by the downcutting Cañada del Oro and its tributaries. “This field examination reveals the fault to have left a sparse but diverse collection of remains implying a varied history of fault development and evolution”, says Hoxie. In detailed mapping of the trace of the Pirate fault zone, he identified a number of sites of exposed fault rocks and fault-related features, ten of which are described in detail. Key observations include identifying local, hematite-rich zones and noting the presence of small-volume, mafic dikes that intruded fault breccia near the end of active uplift on the Pirate fault.

The report includes an annotated satellite image of the Santa Catalina Mountains – Cañada del Oro Basin and a suite of maps showing the distribution of geologic units – alluvium, granites (emplaced between about 70 to 26 million years before the present), and the Pinal Schist, a 1.6 billion-year-old metamorphic rock – that crop out along the fault.

Pirate-fault-outcrop-300x257The photo on the left shows an outcrop of the steeply dipping Pirate fault. The photo above shows several faults in the Santa Catalina Mountains including the Catalina detachment fault which forms the scarp on the north side of Tucson.

 

Tucson solar project not a good deal for taxpayers

Two years ago the City of Tucson began installing solar systems on City properties. Now those installations are ready to produce electricity. The City touted the project as saving money in electricity costs and generating revenue. On its face that would seem to be a good deal, but the details leave questions.

The project was financed by selling $11.2 million worth of “Clean Renewable Energy Bonds.” According to City Energy Manager Douglas Crockett, these bonds carry an annual interest rate of 1.97%. That means taxpayers will have to pay $220,640 in interest each year for a total of $5,516,000 in interest over the 25-year project life. Since those bonds will eventually have to be paid back, total cost the taxpayers (or ratepayers) is therefore $16,716,000.

The City estimates electricity cost savings of $3.9 million over the life of the project. They also claim the project will produce $6.2 million in revenue over the next 25 years. Savings plus revenue to the City total $10.1 million, but the taxpayer cost is $16,710,000 (interest plus principal). It appears that taxpayers would have been better off had the project not been built. If my perception of this project is in error, I would like a detailed explanation by the City explaining why the project is good for taxpayers.

This project seems to me to be another simple-minded, politically correct ploy to appear “sustainable” much like the $196 million the City is spending to build their 3.9-mile long, 19th century concept, “modern street car.”

The Pontatoc mine in a north Tucson neighborhood

Sometimes mines just vanish.  Such seems to be the case with the Pontatoc mine located near the north end of Pontatoc Road in Tucson and just south of Pontatoc Ridge.  The map below shows the general location (at the balloon).

 Pontatoc general locationThe Pontatoc mine was discovered in 1906 and worked until 1917.  It produced about 5,000 tons of copper, silver, gold, and molybdenum ore.  Mindat.org reports that handpicked ore assayed at 4% copper, 0.5 oz./T silver, and a trace of gold.

Mineralization occurred  in a wide altered breccia zone along the Catalina foothill fault dividing Catalina Gneiss, a Laramide metamorphic, from Tertiary to Quaternary Pantano conglomerate beds. “Ore occurred in the fault zones wherever rock alteration is intense. Alteration included silicification, propylitization, spordic dolomitization and epidote. Sulfides precipitated with quartz,” according to Mindat.org.

Workings consisted of two shafts, one 105 feet deep, the other 125 feet deep, plus a pit and tunnel operations.  The following graphic from the Pusch Ridge wilderness study by George S. Ryan  shows again the general location and location of mine workings on Pontatoc Ridge to the north.

Pontatoc-USBM

According to Ryan, Pontatoc Ridge was intensely prospected shortly after the production from the Pontatoc mine itself.  There were several shows of oxide copper on the ridge, but apparently they didn’t amount to much.

So far I’ve shown rather vague locations for the Pontatoc mine and it may surprise you where it was.  The map below shows the mine location with current development.

The following graphics show where I think the mine was, just west of the intersection of E. La Paloma Dr. and E Coronado Dr.  There is no trace of the pit or shafts, presumably they have been filled in. The detailed picture does show what is presumably the scarp of the fault in which the mineralization developed.

Pontatoc-location

Some mines just disappear and houses are built along or near fault zones.  This particular fault is apparently inactive, homeowners shouldn’t worry.

By the way, Ryan reports that gypsum was mined from Tertiary lake beds in the same area and used  for plaster in the Tucson building industry prior to 1966.

pontatoc-built-location

Pontatoc-detail1

References:

Ryan, George S., 1982, Mineral Resources  Investigation  of the Pusch Ridge Wilderness

Pima  County,  Arizona, U.S.B.M. open file report MLA  118-82.

http://www.mindat.org/loc-35539.html (Note this reference erroneously lists the Township as 12S rather than 13S.)

See also:

Florence Copper another mining controversy

Gold in Arizona

Gold of Cañada del Oro and rumors of treasure

Old mines of the Tucson Mountains

Oracle Ridge Mine on Mount Lemmon

Sierrita Mine is only U.S. source of Rhenium

The I-10 copper deposit